(2:30 p.m. EST) -- More than a week after a devastating earthquake and tsunami struck Japan's northern coast, Princess Cruises has decided to scrap port calls to the island nation through May.

There is one exception: The line's Ocean Princess, which departs Shanghai on April 13, will still visit Okinawa (the most southern prefecture) on April 15.

Sun Princess, set to arrive in Japan on March 28, is the first of the Princess ships affected by the changes. Calls in Nagasaki, Osaka, Yokohama and Iwo Jima have been replaced by extra sea days and calls in Tianjin, China, and Busan, South Korea. Similarly, Diamond Princess, which departed Singapore on March 19, will now stop in Busan rather than Nagasaki on April 1.

The line, which said in a statement on its Web site that it's notifying passengers of all impending itinerary changes, made the decision "after careful review of the evolving situation and guided by the U.S. Department of State and other authorities."

Royal Caribbean. Legend of the Seas -- Royal Caribbean's year-round, Asia-based ship -- skipped its scheduled call in Fukoka on March 16. The ship proceeded directly to Busan, its next scheduled call. Legend's following sailing, which departed Shanghai on March 19, was also altered. The ship called on Cheju Island, South Korea, on March 20 and will stay overnight in Hong Kong from 8 p.m. March 22 until midnight on March 23. Legend of the Seas will return to Shanghai on Saturday, March 26, as scheduled. Legend was originally set to visit three Japanese ports -- Kagoshima, Beppu and Fukuoka.

In a statement, the line said that it has "been closely monitoring the situation in Japan since the earthquake and tsunami, especially the status of the damaged nuclear reactors. We are aware that several countries have issued advisories discouraging travel to Japan, and many of our guests have expressed concern about whether it is safe to call there."

Passengers who chose to sail on the revised itinerary will receive an onboard credit. Guests who chose not to sail on March 19 will receive a full refund.

No additional announcements have been made about Legend's future cruises.

Oceania Cruises. Oceania's Nautica, which is currently in the middle of a 15-night Far East cruise, bypassed several Japanese calls. Spokesman Tim Rubacky called the decision the "prudent thing to do" in light of the "Japanese government focusing all available resources on the rescue and recovery effort." The new itinerary replaced stops in Hiroshima and Kobe with additional days in Shanghai and Kaohsiung and an overnight stay in Hong Kong at the tail end of the voyage. The ship's March 22 call in Okinawa remains unchanged.

Although cruise ports haven't sustained notable damage, the U.S. Department of State has issued a travel warning, which "strongly urges U.S. citizens to defer travel to Japan at this time and those in Japan should consider departing."